You set the temperature, the unit hums along, and days later the water is still cold. A pool heat pump that runs but doesn’t heat is one of the most common calls we take, and it’s also one of the most misdiagnosed. Plenty of units get written off as dead when the actual problem is a cheap component, a blocked filter, or nothing at all.
Winter is when these problems tend to surface. A heat pump works hardest when the air is coldest, so a unit that limped through summer with a marginal fault will often give up around now, right when owners are thinking about getting the pool ready for spring.
Here’s how to tell the difference between a genuine fault, a maintenance issue, and a unit that is simply doing what it was designed to do.
First, Check Your Pool Heat Pump Isn’t Behaving Exactly as Designed
Before assuming the worst, rule out these four situations. They account for a large share of the “it’s broken” calls we attend.
The Air Temperature Has Dropped
A pool heat pump doesn’t create heat. It extracts warmth from the outside air and transfers it into your water, which is why it uses so much less energy than gas or electric element heating. As the Australian Government’s Your Home guide explains, heat pumps shift heat rather than generate it, and that makes them very efficient.
The trade-off is that performance is tied to air temperature. On a cold, still morning there is simply less heat available to move, so the unit works harder and heats more slowly. That’s physics, not a fault.
You’re Expecting Heat Too Quickly
Heat pumps warm water gradually. Depending on pool size, starting temperature, air temperature and whether a cover is used, expect roughly 24 to 72 hours to bring a pool up to a comfortable temperature from cold. If you switched it on yesterday and the water feels unchanged today, it may be working normally.
The Pool Has No Cover
This is the single biggest cause of “my pool heat pump can’t keep up”. An uncovered pool sheds heat overnight through evaporation, and the unit spends the next day recovering ground it lost while you slept. Energy.gov.au notes that a good cover can cut heat loss from a heated pool by as much as 75%. Without one, even a correctly sized and perfectly healthy unit will struggle. We’ve covered this in more detail in our guide on whether you really need a pool cover with a heat pump.
The Filtration Pump Isn’t Running Long Enough
Your heat pump can only heat water that is moving through it. If the filtration pump’s timer has been shortened, or the two are running on mismatched schedules, the heater may only be getting an hour or two of circulation a day. Check that the filter pump runs while the heater is calling for heat.
Common Pool Heat Pump Faults and What They Mean
If the basics check out, you’re likely looking at a genuine fault. These are the ones we see most often.
The Unit Runs but the Water Never Warms
When everything appears to be operating and the water temperature won’t lift, the usual culprit is low refrigerant charge caused by a leak. Refrigerant isn’t consumed in normal use, so a low charge always means it has escaped somewhere. Topping it up without finding the leak is a short-term fix at best, and it is also poor practice environmentally.
Ice or Heavy Frost on the Evaporator Coil
Some light frosting in cold weather is normal and the unit should defrost itself. Persistent, heavy icing is not. It usually points to low refrigerant, restricted airflow across the coil, or a failed defrost sensor. Running a heavily iced unit can damage the compressor, so switch it off and book a service.
The Fan Spins but There’s No Heat
This often indicates the compressor isn’t starting. A failed run capacitor is a frequent and relatively inexpensive cause, and it is exactly the sort of part that gets a unit condemned unnecessarily. A failed compressor is the more serious possibility.
An Error Code Appears on the Controller
Most modern units display a fault code rather than simply stopping. Codes vary between brands, and the same code can mean different things on a Rheem, Madimack, Astral or Evo Heat unit. Common causes behind them include water flow faults, high or low pressure trips, and outgoing water temperature sensor faults. Photograph the code before you switch the unit off, because it saves diagnostic time and often tells the technician which part to bring.
The Unit Starts, Then Shuts Down After a Few Minutes
Short cycling like this usually relates to water flow or pressure. A blocked filter, closed valve, low water level, faulty flow switch or failing pressure sensor will all trip the unit off as a protective measure. The heater is protecting itself, which is a good sign that its safety controls are working.
The Unit Won’t Power Up at All
Check the isolator switch and the circuit breaker at the switchboard first. If the breaker has tripped, don’t simply keep resetting it. A repeatedly tripping breaker signals an electrical fault that needs investigating.
A New or Unusual Noise
Rattling often means loose panels or fan blade damage. Grinding or screeching typically points to fan motor bearings. A sudden change in the noise a unit makes is worth acting on early, because bearing failures tend to take other components with them.
What You Can Safely Check Yourself
There is a short list of things any pool owner can check before calling anyone:
- Water level, which should sit at the middle of the skimmer
- Filter cartridge or basket for blockages
- Valve positions, particularly if anyone has been servicing the pool
- Filtration pump timer settings and run times
- Set temperature on the controller, and that the unit is in heat mode rather than an automatic or cooling mode
- Airflow around the unit, with at least the manufacturer’s recommended clearance and no shrubs, fencing or stored items restricting it
- The error code on the display, photographed for reference
That’s the safe list. Everything past it involves refrigerant, electrical components, or both.
Where the Line Is: What Needs a Licensed Technician
In Australia, handling refrigerant is not a matter of preference or confidence. Anyone working with regulated refrigerants must hold a Refrigerant Handling Licence issued by the Australian Refrigeration Council, a legal requirement under federal environmental legislation. Pool heat pumps also combine water and mains electricity, which makes unlicensed poking around genuinely dangerous.
If the fault involves refrigerant, the compressor, the electrical circuit or internal sensors, it needs a licensed refrigeration technician.
Why a Faulty Pool Heat Pump Doesn’t Always Need Replacing
Here’s the part worth knowing. Many pool companies install heat pumps but have never been trained to repair one, because pool servicing and refrigeration are different trades. When those businesses are called to a faulty unit, replacement is often the only answer they can offer.
A refrigeration-qualified technician can diagnose the actual failure and, in many cases, replace a capacitor, sensor, fan motor or control board for a fraction of the cost of a new system. We carry common breakdown parts in our vehicles specifically so that most repairs are completed on the first visit, instead of leaving you waiting weeks for a part to arrive.
Preventing the Next Breakdown
Most heat pump failures give warning signs, and most are cheaper to address early. We recommend an annual service for residential units, and quarterly servicing for commercial installations such as learn-to-swim centres, gyms and aquatic facilities, where units run far harder and downtime costs bookings.
Between services, keep the area around the unit clear, maintain your filtration, and use a cover.
Book a Pool Heat Pump Repair
If your unit is showing any of the faults above, our team services Sydney, Western Sydney and the Blue Mountains for pool heater and heat pump repairs, on residential and commercial systems alike. You can also read more about the pool heat pump brands we install and service.
Contact our team today or request a callback, and have your error code handy if the unit is displaying one.
